CMA Fixed Extension Columns can be used with any 1 12 NPT accessory to lower projector to desired height. Consists of 1 12 NPT column threaded on both ends 3 to 6'lengths.CMA Fixed Extension Columns can be used with any 1 12 NPT accessory to lower projector to desired height. Consists of 1 12 NPT column threaded on both ends 3 to 6'lengths.500 lbs. Weight Capacity